The present invention relates to indicators of surface preparation and methods of making such indicators.
Typically, the application of coatings to a surface of a substrate requires proper surface preparation to provide adequate bonding between the coating and the surface. Examples of such coatings include paints, adhesives, primers, and the like. Surface preparation is performed to remove surface contaminates such as dust, fluids, oils, dirt, and the like, to obtain a desired surface cleanliness and/or to improve adhesion of the coating to the surface. A properly prepared surface may also be contaminated prior to the application of the coating. It would be desirable to provide an easy, inexpensive way of testing a surface just prior to the application of a coating or adherent to determine if additional surface preparation is required to provide an adequate bond between the surface and the coating.
In one embodiment, the invention provides a method of directly indicating the propensity of an adherent or coating to bond to a surface of a substrate. The steps of the method comprise applying a surface preparation indicator to the surface of the substrate wherein the substrate has a desired or target adhesion force to a coating. The surface preparation indicator comprises a polymeric backing material having a yield point and an adhesive on the backing. The target adhesive force and the force required to reach the yield point of the indicator are substantially the same.
In another embodiment, the invention provides a method of designing a surface preparation indicator for a particular substrate and adherent or coating combination. This method comprises the steps of providing a target adhesion force for the adherent to an acceptable surface of a substrate; selecting an adhesive that provides an adhesion to the acceptable surface that is equal to or greater than the target adhesion force and that provides an adhesion that is less than the target adhesion force when the surface of the substrate is not acceptable; selecting a backing material having a yield point and that bonds to the selected adhesive such that the backing material and the adhesive will not separate when subject to applied force that is lower than that of the target adhesion force; configuring said backing material such that the applied force required to reach the yield point is substantially the same as the target adhesion force; and bonding the selected adhesive to the backing material.
A xe2x80x9cyield pointxe2x80x9d is the point at which, after an initial applied stress, a further applied stress causes appreciable elongation or yield in a material without the application of comparable additional stress. In other words, a xe2x80x9cyield pointxe2x80x9d is the point at which, after an initial applied stress, appreciable elongation or yield in a material is obtained without the application of comparable additional stress. A material stressed beyond its yield point will have permanent deformation.
xe2x80x9cAdhesivexe2x80x9d means any substance that is capable of bonding to other materials by surface attachment.